1. Field of the Invention
The present invention relates to an image processing apparatus, an image forming apparatus, and image processing method for applying image processing to image data so as to accomplish proper image formation. More particularly, it relates to an image processing apparatus, an image forming apparatus, and image processing method for discriminating a halftone dot region in an image so as to apply particular processing such as moiré prevention to the halftone dot region.
2. Description of Related Art
For image processing of a halftone dot region, conventional image processing apparatuses such as digital copier, printer, and the like, have applied particular processing such as smoothing and the like that is different from processing of other regions. That is, in the halftone dot region, moiré can occur due to interference of read resolution and halftone dot frequency. When moiré occurs, quality of image deteriorates. Therefore, it is necessary to prevent moiré from occurring. Japanese laid-open patent application No. 8-181864 discloses such type of image processing. An image processing apparatus directed to No. 8-181864 detects mountain peaks and valley peaks in image data (in this specification, these peaks are generally termed isolated points). By treating density of those peaks as index of halftone dot degree, there is detected what extent density of halftone dots is formed with a pixel and vicinity of the pixel.
However, in case an image such as a character, a figure, or the like, exists near isolated points, the image processing apparatus directed to No. 8-181864 cannot separate the character region and isolated points appropriately. As a result, particular image processing to be applied to a halftone dot region is erroneously applied to a character and the like arranged near isolated points.